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RCW 86: Historical Supernova Remnant

Explanation: In 185 AD, Chinese astronomers recorded the appearance of a new star in the Nanmen asterism. That part of the sky is identified with Alpha and Beta Centauri on modern star charts. The new star was visible to the naked-eye for months, and is now thought to be the earliest recorded supernova. This deep telescopic view reveals the wispy outlines of emission nebula RCW 86, just visible against the starry background, understood to be the remnant of that stellar explosion. Captured by the wide-field Dark Energy Camera operating at Cerro Tololo Inter-American Observatory in Chile, the image traces the full extent of a ragged shell of gas ionized by the still expanding shock wave. Space-based images indicate an abundance of the element iron in RCW 86 and the absence of a neutron star or pulsar within the remnant, suggesting that the original supernova was Type Ia. Unlike the core collapse supernova explosion of a massive star, a Type Ia supernova is a thermonuclear detonation on a white dwarf star that accretes material from a companion in a binary star system. Near the plane of our Milky Way galaxy and larger than the full moon on the sky this supernova remnant is too faint to be seen by eye though. RCW 86 is some 8,000 light-years distant and around 100 light-years across.

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The supernova remnant RCW 86 did not come from the Chinese Guest Star of 185 AD, and the Guest Star is not from a supernova:

RCW is much older than 1838 years (2023-185). One quick way to see this is to take the caption's quoted size of 100 lightyears (50 ly radius) to calculate the average velocity in 1838 years of 50/1838 = 0.027 times the speed of light, or 8200 km/s. The problem is that 8200 km/s is typical for the velocity at the initial ejection, whereas the ejecta slows down greatly over 1838 years as a stiff power law, so the *average* velocity over 1838 years must be <<8200 km/s. Indeed, the current expansion velocity of RCW 86, as based on the observed proper motion of the remnant (Helder et al. 2013, MNRAS, 435, 910) is 1200 +- 200 km/s. With this, there is no way that the SN of RCW 86 could possibly have been in the year 185 AD.

The Guest Star of 185 AD was not a supernova. The only information about the Guest Star is 50 Chinese characters written c. 300 AD (i.e., 115 years later), with this then further edited in c. 510 AD into a compilation by historians writing the dynastic history of the Later Han Dynasty (the Houhanshu), placing together scattered and brief Imperial records covering several centuries of observations. The *only* evidence that the Guest Star of 185 AD is a supernova is that its duration is long. The star was first reported on 7 December 185, and the disappearance was in the 6th month of the "hounian" year. In ancient Chinese, "hounian" is ambiguous and might mean in 'several years', or it might mean 'next year' with or without inclusive counting. So the disappearance might have been in the sixth month of 186, or 187, or 188 AD. In all these cases, the reported duration of visibility is sufficiently long that a supernova is the only single possibility. (See my similar argument for the case of the Guest Star of 1181 AD being a supernova, in Schaefer 2023, arXiv:2301.04807.) The problem to get the long duration is the requirement that the event in December of 185 must be from the same source as for the reported disappearance in the sixth month of 186/187/188. For this, the Chinese elsewhere recorded the disappearance of a very bright and famous comet in the sixth month of 188 AD in the exact same area of the sky. The comet is P/Swift-Tuttle, the parent comet of the Perseid meteor shower. (Note; APOD will certainly carry pictures of this comet during its close encounter, at 0.153 AU from Earth, on 5 August 2026, reaching near zeroth magnitude.) The coincidence of the known bright comet disappearing at the same time and place as the reported disappearance of the Guest Star is too much, unless there is a causal connection. The causal connection is that the compiler in the year 300 AD took a report of a Guest Star in 185 AD and connected it with the Guest Star in the sixth month of 188 AD that occurred in the same area of the sky. (The December 185 event was most likely an ordinary galactic nova, or even possibly the formation of the giant shell of He 2-111.) Such concatenations of separate events are common in the Chinese dynastic annals, as the compilers only had sketchy reports centuries old that they were trying to form into a coherent account. Such concatenations are reported for for records in 837, 838, and 1592, as well as possibly in 238 BC, AD 277, 902, and 1506. So we have a simple and inevitable case that the Guest Star of 185 is really two separate events (Schaefer 1995, AJ, 110, 1793). This breaks the long duration. And with the long duration gone, we have no evidence that the event was a supernova of any kind.

I think it would be more accurate to refer to them as Chinese ASTROLOGERS, rather than astronomers, because that is what they were.

Brad Schaefer wrote: ↑Fri Mar 03, 2023 10:07 am The supernova remnant RCW 86 did not come from the Chinese Guest Star of 185 AD, and the Guest Star is not from a supernova:
RCW is much older than 1838 years (2023-185). One quick way to see this is to take the caption's quoted size of 100 lightyears (50 ly radius) to calculate the average velocity in 1838 years of 50/1838 = 0.027 times the speed of light, or 8200 km/s. The problem is that 8200 km/s is typical for the velocity at the initial ejection, whereas the ejecta slows down greatly over 1838 years as a stiff power law, so the *average* velocity over 1838 years must be <<8200 km/s. Indeed, the current expansion velocity of RCW 86, as based on the observed proper motion of the remnant (Helder et al. 2013, MNRAS, 435, 910) is 1200 +- 200 km/s. With this, there is no way that the SN of RCW 86 could possibly have been in the year 185 AD.

Thanks for your great historical expertise.

But I don't believe that this is a classic linear expansion.
Please read: viewtopic.php?t=42410

"We report the discovery of a solar-type star in a close, eccentric binary system with a neutron star within the young Galactic supernova remnant RCW 86. Our discovery implies that the supernova progenitor was a moving star, which exploded near the edge of its wind bubble and lost most of its initial mass due to common-envelope evolution shortly before core collapse. We find that the solar-type star is strongly polluted with calcium and other elements, which places the explosion within the class of calcium-rich supernovae – faint and fast transients, whose origin is strongly debated, and provides the first observational evidence that supernovae of this type can arise from core-collapse explosions." https://arxiv.org/abs/1702.00936






https://www.flickr.com/photos/185130090 ... 1/sizes/o/
Original data: NASA/JPL-Caltech/B. Williams (NCSU)


https://live.staticflickr.com/65535/527 ... f95c_o.jpg
Original data: NASA/JPL-Caltech/B. Williams (NCSU)


jac berne (flickr)

AVAO wrote: ↑Fri Mar 03, 2023 5:26 pm

Brad Schaefer wrote: ↑Fri Mar 03, 2023 10:07 am The supernova remnant RCW 86 did not come from the Chinese Guest Star of 185 AD, and the Guest Star is not from a supernova:
RCW is much older than 1838 years (2023-185). One quick way to see this is to take the caption's quoted size of 100 lightyears (50 ly radius) to calculate the average velocity in 1838 years of 50/1838 = 0.027 times the speed of light, or 8200 km/s. The problem is that 8200 km/s is typical for the velocity at the initial ejection, whereas the ejecta slows down greatly over 1838 years as a stiff power law, so the *average* velocity over 1838 years must be <<8200 km/s. Indeed, the current expansion velocity of RCW 86, as based on the observed proper motion of the remnant (Helder et al. 2013, MNRAS, 435, 910) is 1200 +- 200 km/s. With this, there is no way that the SN of RCW 86 could possibly have been in the year 185 AD.

Thanks for your great historical expertise.

But I don't believe that this is a classic linear expansion.
Please read: viewtopic.php?t=42410

"We report the discovery of a solar-type star in a close, eccentric binary system with a neutron star within the young Galactic supernova remnant RCW 86. Our discovery implies that the supernova progenitor was a moving star, which exploded near the edge of its wind bubble and lost most of its initial mass due to common-envelope evolution shortly before core collapse. We find that the solar-type star is strongly polluted with calcium and other elements, which places the explosion within the class of calcium-rich supernovae – faint and fast transients, whose origin is strongly debated, and provides the first observational evidence that supernovae of this type can arise from core-collapse explosions." https://arxiv.org/abs/1702.00936






https://www.flickr.com/photos/185130090 ... 1/sizes/o/


https://live.staticflickr.com/65535/527 ... f95c_o.jpg


jac berne (flickr)

Thanks, AVAO, that's so very very interesting!!

And this would explain why one part of the supernova shell is no much brighter than the rest of the shell:


This part of the shell is so bright because here is where you find the neutron star pushing out of its own shell due to the fact that the supernova progenitor was already moving in this direction when it exploded as a supernova.

My own annotated version of today's APOD pales in comparison with the hugely fascinating identification of the neutron star that was created by the supernova of 185 A.D, but I'll post my annotated picture anyway. A number of foreground stars appear to follow the outline of the supernova shell (which is of course an illusion). The stars are of various spectral classes, various luminosities and are found at various distances:


Ann

Interesting that this, or these, issues are up for debate instead of settled science - realizing of course that "settled science" can in so many cases be an oxymoron. Perhaps Chris can elucidate, as he is so well-informed, careful, and exact...

And for those who dare, Happy Messier Marathon Stargazing, coming soon to a sky near you!

zendae wrote: ↑Fri Mar 03, 2023 7:12 pm Interesting that this, or these, issues are up for debate instead of settled science - realizing of course that "settled science" can in so many cases be an oxymoron. Perhaps Chris can elucidate, as he is so well-informed, careful, and exact...

Well. I don't understand what's so unscientific about the discussion. In my opinion, Brad Schaefer's explanatory models and that of the arxiv paper (https://arxiv.org/abs/1702.00936) contradict each other. My statement is only that I consider the explanatory model of the scientific arxiv paper to be more plausible?

Not much left of this nova; just a few wispy remnants!

zendae wrote: ↑Fri Mar 03, 2023 7:12 pm Interesting that this, or these, issues are up for debate instead of settled science - realizing of course that "settled science" can in so many cases be an oxymoron. Perhaps Chris can elucidate, as he is so well-informed, careful, and exact...

And for those who dare, Happy Messier Marathon Stargazing, coming soon to a sky near you!

Science, unlike religion, is always "up for debate".

Some things are settled. Such as the fact that the Earth is spherical, not flat, and it doesn't have an edge that we can fall off of. And the theory of the Big Bang is extremely robust, and what is up for debate is details of exactly when it happened, and the conditions inside the very early Universe that it created, etcetera.

So the fact that we are debating the nature of a distant nova shell and what created it does not undermine science. Quite the opposite.

Saying that God or aliens created it would be the opposite of science, and it would turn us humans into children telling fairy tales about the Universe instead of trying to understand it.

Ann

Ann wrote: ↑Sat Mar 04, 2023 5:05 am

zendae wrote: ↑Fri Mar 03, 2023 7:12 pm Interesting that this, or these, issues are up for debate instead of settled science - realizing of course that "settled science" can in so many cases be an oxymoron. Perhaps Chris can elucidate, as he is so well-informed, careful, and exact...

And for those who dare, Happy Messier Marathon Stargazing, coming soon to a sky near you!

Science, unlike religion, is always "up for debate".

Some things are settled. Such as the fact that the Earth is spherical, not flat, and it doesn't have an edge that we can fall off of. And the theory of the Big Bang is extremely robust, and what is up for debate is details of exactly when it happened, and the conditions inside the very early Universe that it created, etcetera.

So the fact that we are debating the nature of a distant nova shell and what created it does not undermine science. Quite the opposite.

Saying that God or aliens created it would be the opposite of science, and it would turn us humans into children telling fairy tales about the Universe instead of trying to understand it.

Ann

"Settled" generally just means that a theory is so well supported and has such a significant consensus that people are no longer investing much (or any) time in exploring alternatives. It's a way of saying something is a fact beyond reasonable doubt. It doesn't mean that some new piece of evidence won't come along that causes a re-evaluation. But that's very unlikely.

orin stepanek wrote: ↑Sat Mar 04, 2023 1:03 am noirlab2307a1024c.jpg
Not much left of this nova; just a few wispy remnants!

Now we need to think of something that was there and that did not left much of itself.

Were it a pair of stars, some 2-3 suns mass each?
One had been the first to fuse all the hydrogen in its core, then for a thousand years it formed a denser core, fused helium, became a red giant, shed its envelope and came to rest as a white dwarf.
After a billion years the other companion became a red giant, fed a lot to the white dwarf and detonated there a fusion of carbon, nitrogen, oxygen and so on. That blast was vast, a supernova, and it kicked the red giants core and envelope, and those keep on moving then and now.

Or was it a merger of two white dwarfs? Then one would became supernova and the other would be partly spent in the fusion and partly kicked out of the merger.

VictorBorun wrote: ↑Sat Mar 04, 2023 9:59 pm

orin stepanek wrote: ↑Sat Mar 04, 2023 1:03 am noirlab2307a1024c.jpg
Not much left of this nova; just a few wispy remnants!

Now we need to think of something that was there and that did not left much of itself.

Were it a pair of stars, some 2-3 suns mass each?
One had been the first to fuse all the hydrogen in its core, then for a thousand years it formed a denser core, fused helium, became a red giant, shed its envelope and came to rest as a white dwarf.
After a billion years the other companion became a red giant, fed a lot to the white dwarf and detonated there a fusion of carbon, nitrogen, oxygen and so on. That blast was vast, a supernova, and it kicked the red giants core and envelope, and those keep on moving then and now.

Or was it a merger of two white dwarfs? Then one would became supernova and the other would be partly spent in the fusion and partly kicked out of the merger.

Check out AVAO's post.

In his post, AVAO quotes the abstract of a paper whose full text you can read here. But the most important tidbit from the abstract (in my opinion) reads like this:

V.V. Gvaramadze, N. Langer, L. Fossati, D.C.-J. Bock, N. Castro, I.Y. Georgiev, J. Greiner, S. Johnston, A. Rau, T.M. Tauris wrote:

When a massive star in a binary system explodes as a supernova its companion star may be polluted with heavy elements from the supernova ejecta. Such a pollution had been detected in a handful of post-supernova binaries (Gonzalez Hernandez et al. 2011), but none of them is associated with a supernova remnant. We report the discovery of a solar-type star in a close, eccentric binary system with a neutron star within the young Galactic supernova remnant RCW 86. Our discovery implies that the supernova progenitor was a moving star, which exploded near the edge of its wind bubble and lost most of its initial mass due to common-envelope evolution shortly before core collapse.

So V.V. Gvaramadze et al. have found a neutron star inside RCW 86. This very strongly suggests that the star that exploded was massive, and that the supernova was of the core-collapse type (which is to say that no white dwarf was involved in the explosion ).


But the star that exploded had a G-type (Sun-like) companion , and the now-neutron star and the G-type companion are still orbiting one another. The supernova progenitor lost most of its mass before it exploded due to interactions with its companion star.

V.V. Gvaramadze et al. wrote:

The fact that the binary system remained bound after the SN explosion, and assuming the standard mass of a NS of 1.4 M⊙, implies a mass of the SN ejecta of less than 2.3 M⊙ — provided that the SN explosion was symmetric — and a mass of the exploding star below 3.7 M⊙. This in turn implies that the SN explosion was of Type Ib and that the initial mass of the primary star was smaller than 13 M⊙.

What the authors are saying here is that the supernova progenitor at the time when it exploded had a mass of only 3.7 solar masses. They also say that the supernova progenitor started out with a mass of no more than 13 solar masses. This implies that the SN progenitor lost up to ~ 9 solar masses due to interactions with its companion before exploding.


(I might add that astronomers believe that a core collapse supernova must come from a progenitor that starts out with no less than 8 solar masses.)

Anyway. V.V. Gvaramadze claimed that the supernova that left behind the neutron star inside RCW 86 must have been a supernova of type Ib.

Wikipedia wrote about SN Ib (and Ic):

Type Ib and Type Ic supernovae are categories of supernovae that are caused by the stellar core collapse of massive stars. These stars have shed or been stripped of their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon. Compared to Type Ib, Type Ic supernovae are hypothesized to have lost more of their initial envelope, including most of their helium. The two types are usually referred to as stripped core-collapse supernovae.

Ann

wow! I could never read that much into this old nova!